Solid ultrasonic delay lines and glass compositions therefor

ABSTRACT

Solid ultrasonic delay lines are provided including an input transducer for converting electrical energy to acoustical energy, an output transducer for converting the acoustical energy to electric energy, and a glass delay line medium located therebetween as a delay line, the glass having a composition comprising the following ingredients in approximate molar amounts: Ingredients Moles SiO2 3.55 to 6.0Al2O3 1RO 1 where R is a divalent metal such as magnesium, cadmium and lead.

United States Patent Field 1451 Jan. 1, 1974 [54] SOLID ULTRASONIC DELAY LINES AND 3,496,401 2/1970 Dumbaugh,.lr 106/52 GLASS COMPOSITIONS THEREFOR 3,402,055 9/1968 Harris et a1. 106/52 [75] Inventor: Marshall Field, Toledo, Ohio FOREIGN PATENTS O PP CATlONS ss g O s i is, Inc, o France [22] Filed: July 1971 Primary Examiner--A. B. Curtis [21] l 1 0 1 4 Assistant Examiner-Mark Bell Attorney-Richard D. l-leberling Related US. Application Data [62] Division of Ser, No. 887,264, Dec. 22, 1969. [57] ABSTRACT [52] US. Cl 333/30 R, 106/52, 106/53 Solid ultrasonic delay lines are provided including an [51] Int. Cl. H03h 7/30, C03 3/30, C03 3/10 input transducer for converting electrical energy to [58] Field of Search 106/52, 53 acoustical gy, an Output transducer for Converting the acoustical energy to electric energy, and a glass [56] Refe e Cit d delay line medium located therebetween as a delay UNITED STATES PATENTS line, the glass having a composition comprising the 3,154,425 10/1964 Hoover et a1. 106/53 followmg mgredlemrs vampoumsz 3,598,619 8/1971 Mikoda et a1 106/53 Tl INGREDIENTS TN MOLES 3,651,431 3/1972 Krause i 106/53 3,669,697 6/1972 Drake i 106/53 810; 3.551060 3,672,921 6/1972 Asahara ct a1...i 106 53 5 1 3,687,697 8/1972 Faulstich et a1. 106/53 1 I r Lem.

- 2 where R is a divalent metal such as magnesium, cad- V V n rson mium and lead.

4 Claims, 2 Drawing Figures SOLID ULTRASONIC DELAY LINES AND GLASS COMPOSITIONS THEREFOR The present application is a division of application S.N. 887,264 filed Dec. 22, 1969, now abandoned.

THE INVENTION The present invention relates to solid ultrasonic delay lines that include a glass delay line medium located between an input transducer for converting electrical energy to acoustic energy and an output transducer for converting acoustic energy to electrical energy. The invention more particularly relates to an ultrasonic delay line with an aluminosilicate glass delay line medium located between the input transducer and the output transducer.

In the past, alkali-lead-silicate glass composition delay line mediums have been used in ultrasonic delay lines, but such compositions have been difficult to melt and have not been as stable in regard to temperature and time as desired for most applications.

It is an object of the present invention to provide an ultrasonic delay line having an acoustic aluminosilicate glass delay line medium located between an input transducer for converting electrical energy to acoustic energy and an output transducer for converting acoustic energy to electrical energy.

It is an object of the present invention to provide an ultrasonic delay line having a glass delay line medium in which the glass composition comprises about 1 mole of A1 1 mole of RO, where R is a divalent metal,-

Ingredients Moles Si0 3.55 to 6.0 A1 0 l RO I where R0 is a divalent metal oxide.

These and other objects will be apparent from the description that follows, the appended claims and the drawings in which:

FIG. 1 is a graph plotting the temperature coefficient of time delay versus the amount of SiO expressed in mole fraction of the total composition showing glass compositions having coefficients of time delays within 8 ppm/C.

FIG. 2 is a schematic view of a delay line assembly employing the glass delay line medium according to the present invention.

As seen in the drawings, a solid ultrasonic delay line assembly includes a glass delay line medium 1, an input transducer 2 for converting electrical energy to acoustic energy, an output transducer 3 for converting acoustic energy to electrical energy, an electrical input circuit 10 with an electrical potential of E volts, and an electrical signal output circuit 12 with an electrical potential of E volts. The glass medium can be a rod or flat polygonal plate or other shape that will transmit the acoustic signal after a desired (delay) time in a desired delayed time interval.

The present invention provides a solid ultrasonic delay line comprising an input transducer for converting electrical energy to acoustic energy, an output transducer for converting acoustic energy to electrical energy, and a glass delay line medium located therebetween, the glass being an aluminosilicate containing about 1 mole of A1 0 1 mole of RO where R is a divalent metal, and about 3.55 to 6.0 moles of SiO On a molar basis, the formula for the glasses of the invention can be written: XRO'YAIgOg'ZSIOg where x/y =1 and z/x+y+z z 0.64 to 0.75.

The present invention provides a solid glass ultrasonic delay line composition, the glass composition being stable, easy to melt and form. The glass delay line medium is used in solid ultrasonic delay lines for television sets, television transmitting studies, small computers, radar range markers (as calibration for use in ships and aircraft) and as memories for oscilloscopes. In addition to being very stable from the time and thermal stability standpoint, the glass delay line medium has other valuable properties that are needed for good ultrasonic delay lines such as low velocity of sound within the medium, low density, excellent small temperature coefficients of time delay in the critical temperature region and a small attenuation (loss factor).

'The velocity of sound generally is less than about 3.9 mm/p. sec and preferably about 2.99 to 3.6 mm/ tsec. The density is generally about 2.3 to 2.8 gm/cc and preferably about 2.5 gm/cc. The attenuation A is low, being low enough for computer memories and low enough for television sets--being less than 1 db/cm at 20 MHZ. The attenuation usually is in the range of less than about 1.2 to 0.9 decibels per centimeter at-20 MHZ. As previously indicated, the temperature coefficients of time delay and the attenuation are also low-- -being preferably less than about 3 ppm/C. and less than about 1 db/cm, respectively. The outstanding compositions of the present invention have excellent temperature coefficients of time delay and as seen in FIG. I, the amount of SiO in mole fraction of the total composition is shown in compositions that provide a certain coefficient of time delay within a i 8 ppm/*C.

By the use of the time delay glass compositions of the present'invention, it is possible to predict and control the temperature coefficient of time delay of the systems over wide ranges of composition. Materials with zero time coefficients of delay can be produced. Advantageously, the glass compositions are easy to form and work with. The densities and delay times can be tailored from the compositions and the compositions can be tailored also to specific criteria of delay time and attenuation.

In the above-described time delay compositions, R is a divalent metal which is preferably an alkaline earth metal such as Mg or Ca. Other metals can be used as R such as Cd, Pb, Fe, Ba and mixtures thereof such as mixtures of Mg and Fe and mixtures of Mg and Ba.

The following examples are intended to illustrate the present invention and not to limit the same.

EXAMPLE A series of aluminosilicate glasses was prepared with varied amounts and kinds of RO oxides. The following glasses were prepared with the oxide content being given in mole percent:

TABLE I Glass Density No. R0 RO M 0 SiO, gm/cm 1 Mn: l7.731 15.284 66.985 2.6864

2 Pb: 17.39 16.743 65.867 3.4538 3 Mg: 8.528 Ba: 8.396 16.719 66.356 2.7613 4 Mg: 16.752 Bi: 8.274 8.465 66.508 3.5512 5 Ca: 16.575 16.800 66.625 2.5431 6 Cd: 10.803 17.944 71.253 2.7725 7 Mg: 8.672 FeO: 6.083 17.014 67.137 2.5925

Fe O z 1.095

In the above Table, R and R are divalent metals.

Another glass, No. 8, which was a potassium-leadsilicate was also prepared, it having the following composition: K O 8.1 weight percent, PbO 43.9 weight percent, Si 47.7 weight percent.

The above materials labeled glass Nos. 1-8 were formed into small cubes and tested, the results which are as follows:

TABLE 11 2O mHz Shear Ultrasonic Data vshear Glass (1/1' )(d'r/dT) (25") No. (ppm/"C.) A(dblcm) mm/usec Cation 1 9.31 1.30 3.6501 Mn 8.14 1.04 3.7018 Ca 3 2154 1.18 3.5309 Mg, Ba 7 1.53 0.89 3.8106 Mg, Fe 2 0.52 1.52 2.9914 Pb 6 1.01 3.5636 Cd 8 3.4 116 2.4733 K The best results were obtained with glasses 3, 6 and 7 which illustrate highly preferred time delay compositions of the present invention.

The above table indicates that glasses 2, 3, 6 and 7 have some properties equal to or superior to those of alkali lead silicate glasses presently used for this purpose. The above properties 'were measured between 24 and 75C., the temperatures commonly encountered in electronic devices. The term 20 MHZ refers to an electrical or elastic wave oscillation frequency of 20 X 10 (sec)". Shear" means a transverse elastic wave. These waves are generated by crystals such as AC cut crystalline quartz when excited with an electric field. The term shear refers to the velocity of shear waves travelling within the sample. This quantity was measured using McSkimins pulse-echo technique. A in decibel per centimeter is measured as times the logarithm of the ratio of the heights of adjacent pulses in the medium divided by the distance traveled, i.e.,

A 1/! '20 log V /V,

where V is the original pulse-height and V is the height of the pulse that has traveled l centimeters through the delay medium. The temperature coefficient of time delay is herein designated:

and is defined as:

l/-r25 dT/dT Ila-(25C.) [1(T) 1(25C.)/T 25].

The last glass, No. 8, was a control glass which represents a potassium-lead-silicate glass of the prior art. The glasses of the present invention have the general composition RO-Al O -xSiO where x generally is about 3.55 to 6 mole and preferably 4.45 to 4.9 moles and such glasses provide outstanding time delay mediums which exhibit (l) exceptionally good temperature and temporal stability, (2) low density, (3) moderate thermal expansion coefficients, (4) acceptable forming properties, and (5) good glass quality substantially free from defects such as seeds.

What is claimed is:

1. A solid ultrasonic delay line comprising an input transducer for converting electrical energy to acoustic energy, an output transducer for converting acoustic energy to electrical energy, and a glass delay line medium located therebetween as a delay line, the glass having a coefficient of time delay of less than i 8 ppm/C. and attenuation less than about 1.2 db/cm at 20Ml-1Z, and having a composition consisting essentially of the following ingredients in approximate molar amounts:

Ingredients Moles SiO 3.55 to 6.0 A1 0,, 1 R0 1 where R is a divalent metal selected from Mg, Ba, Fe or mixtures thereof.

2. A delay line as defined in claim 1 in which the R is an alkaline earth metal.

3. A delay line as defined in claim 1 in which R is Mg.

4. A delay line as defined in claim 1 in which the amount of Si0 in the glass composition is about 4.45

to 4.9 moles. 

2. A delay line as defined in claim 1 in which the R is an alkaline earth metal.
 3. A delay line as defined in claim 1 in which R is Mg.
 4. A delay line as defined in claim 1 in which the amount of SiO2 in the glass composition is about 4.45 to 4.9 moles. 